1. Construction and details of operation of a respiration chamber suitable for studies on the laying hen are described.

2. Calorimetric data on the utilization of food energy from balanced rations and from glucose are given.

3. The net energy of balanced rations for maintenance and production is 83·7% of the metabolizable energy. The figure for glucose is considerably higher.

4. The maintenance requirement of the 2 kg. laying hen is 88·9 kcal. metabolizable energy/kg./day.

5. Some comments are given on the significance of protein metabolism in relation to the use of indirect calorimetry for avian species.

1. The leaf tensile strength of individual plants of a population of Lolium (multiflorum x perenne) perenne was measured on four occasions, October and December 1963 (160 plants) and January and March 1964 (73 of the 160 plants). All plants had been chosen for the good uniform vegetative growth they had exhibited over several seasons. The cellulose content of the 14 weakest and 14 strongest plants in October and of all 73 plants in March was determined.

2. There was a wide range in leaf strength, maintained from October to March, within the population. In October all 14 weakest plants had lower cellulose content than the 14 strongest and from these two groups six plants of low leaf strength and low cellulose content and six of high leaf strength and high cellulose content were selected as parent plants for divergent selections. In March there was a positive highly significant (P < 0.001) phenotypic correlation between leaf strength and cellulose content (r = +0.58).

3. Two diallel crosses were performed, one within the six parents of low leaf strength and low cellulose content and the other within the six high parents. Leaf strength and cellulose data was obtained from progeny and from parental ramets in October 1964 and high overall heritabilities for both characters (approx. 0.8) calculated from achieved advances and parent/progeny regressions. Selection for high leaf strength and high cellulose content was more effective than for low.

1. Young sheep, aged either 2 or 6 months, were fed for various periods on diets low in either phosphorus, vitamin D, phosphorus and vitamin D, or calcium and subsequently for 12 months on control diets.

2. The effects of treatment on the mineral status of the animals were judged by the calcium and phosphorus contents of the blood, the ash contents and radiological appearance of the bones, and the clinical appearance of the limbs. The quality of the teeth produced by each treatment was judged clinically.

Certain relationships between linear live animal and carcass measurements and the quantitative composition of the half-carcass have been established.

Of the live linear body measurements taken, the length of the fore-cannon bone and length of the hind leg appear to have close relationship with carcass measurements. Live fore-cannon bone is a good index of the total weight of bone in the halfcarcass and therefore has application in the selection of meat sheep.

Of the carcass measurements studied, length of fore-cannon bone and length of tibia + tarsus (T) appear to be satisfactory predictors of the total weight of bone.

1. Lucerne was grown in a glasshouse under different moisture regimes in order to determine the effect of soil moisture content at the time of defoliating on subsequent yield.

2. Drought conditions were found to reduce yield in the short-term, particularly in conditions in which demand for water was high, but the crop subsequently recovered when supplied with ample moisture. Defoliation during a drought period showed no long-term effect on yield.

This work was carried out as part of the programme of crop-husbandry experimentation at the University of Cambridge School of Agriculture, and the author welcomes this opportunity of thanking Mr F. Hanley, Reader in Crop Husbandry, for advice and suggestions.

1. In growing sheep fed on a low-calcium diet for 12 months and for a similar period on a diet of adequate mineral content, a tendency for the incisor teeth to protrude beyond the maxillary pad (prognathism) was observed. This arose primarily during the repair period, and was apparently caused by poorer repair of the upper skull than of the mandible. This was not observed in animals fed on a control diet or one deficient in phosphorus and vitamin D.

2. A malocclusion of molar teeth associated with poorly mineralized and extremely weak mandibles, which prevented the incisor teeth from meeting the dental pad, occurred in growing sheep fed for 12 months on a diet deficient in phosphorus and vitamin D. This defect was not observed in similar animals fed on a control diet nor in those fed on a diet of low calcium content. Treatment effects on the shape of the mandible that were apparently related to this malocclusion are described.

A comparison has been made over 2 years of spring shedding in cattle maintained in two environments experiencing a similar photoperiod but vastly different seasonal temperatures. At each location (Walcha and Narrabi, N.S.W.) experimental animals were divided into two nutritional groups, namely a Feed group and a Pasture group.

2. In 1961-62 both the Feed and Pasture groups in the warmer climate of Narrabri shed their winter coats in October, while animals maintained under the cooler conditions of Walcha did not acquire their summer coats until January of the following year. The Narrabri groups, however, also displayed superior live-weight gains than the corresponding groups exposed to the more severe winter conditions prevailing at Walcha.

3. The following year (1962-63) a differential feeding programme was adopted for the two Feed groups which resulted in their live-weight gains for the experiment being similar. Although the low ration of hay fed to the Narrabri Feed group to achieve this parity of weight gains introduced a nutritional stress factor in the group, these animals displayed a slightly superior shedding ability than did those in the Walcha Feed group.

1. The teeth of sheep that had been fed from 6 months of age for 12 months on diets low in calcium or in phosphorus and vitamin D content were compared with those of similar animals fed a control diet.

2. The low calcium diet depressed the development of both dentine and enamel but had a greater effect on enamel than dentine, while the low phosphorus and vitamin D diet depressed dentine development slightly and had practically no effect on enamel.

3. The percentages of ash of the dentine and enamel were not significantly affected by the diets fed.

An experiment was conducted to investigate the relationship between specific gravity and total fat content of the half-carcass. Specific gravity was found to be highly but negatively correlated with the percentage of fat in the half-carcass

(r = −0·9841, P < 0·001).

It was also found that the sample joint is a satisfactory index of fatness of joint as well as that of the half-carcass.

1. Four experiments designed to investigate the effect of fertilizers on the rate of bulking of Majestic potatoes are described and the results discussed.

2. Irrespective of fertilizer application yield increased until the haulm died and then decreased slightly.

3. Sulphate of ammonia increased the yield by increasing the number of tubers and increasing the yield in all size-grades. Thus its effect was seen throughout the season, no matter what grades yield was based on. It also increased dry-matter percentage.

The follicle ratio S/P and the fibre ratio Sf/Pf have been determined for various post-natal ages of English Romney lambs in six lamb crops.

A maximum site-sampling error has been determined for use in assessing the degree of significance of differences in values of the ratio S/P determined from successive skin samples from individual lambs. Variations encountered in these Romney lambs in the level of their follicle and fibre ratios, in their rates of change and in the degree of their association with live-weight changes show that rigid conclusions based on data from one lamb crop only are not justified. An intensive study of birth and 8-day old samples has shown that follicles may regress in the early post-natal life of the lamb.

Not all follicle anlagen are initiated before birth and the ‘ceiling value’ of the adult ratio Sf/Pf is not necessarily determined or set pre-natally except in the sense of there being a genetic maximum which may or may not be attained. Low restricted follicle and fibre ratios at birth may increase rapidly postnatally and high ratios at birth may increase little, if at all, post-natally. The follicle and fibre ratio may increase even between the ages of 6 and 12 months.

1. Radioactive phosphorus was injected into young sheep that had been fed diets low in either phosphorus, phosphorus and vitamin D or calcium. Forty-eight hours after the injection the animals were killed and samples of bone and teeth were removed for specific activity determinations.

2. The specific activities of bone varied according to the site from which it was taken, but in general a strong inverse relationship was found between specific activity and the quality of the skeleton.

3. In teeth that were formed during the period the diets deficient in phosphorus or phosphorus and vitamin D were fed, the specific activities of the dentine and enamel were greater than for corresponding tissues from the control animals.

The paper deals with points arising in the design of factorial schemes for incorporating fertilizer and other treatments in rotation experiments. These schemes make extensive use of fractional replication and confounding, including split-plot confounding. They are complicated by the need to apply some treatments cumulatively and others with levels changed between plots in successive cycles so as to minimize errors due to constant plot differences.

Design keys are used to identify the treatment main effects and rotation differences with particular plot contrasts. The keys exhibit the structure of a design more compactly and clearly than a complete enumeration of identities and confounded contrasts and enable treatment combinations to be generated systematically.

Three series of experiments are described from which minimum estimates of crop loss caused by bacterial blight were obtained. In the first two, the estimates were derived from seed-dressing trials, and in the third, seed dressing was used in conjunction with resistant varieties.

Losses amounted to as much as 354 ± 39 lb. seed cotton/acre for a susceptible variety but could be reduced both by seed dressing and by using resistant varieties. The effectiveness of resistance in moderately resistant varieties varied from one season to the next, an effect comparable with the genotype-environment interactions previously described for reactions to inoculation.

1. Station progeny tests of twenty-four Ayrshire and twenty-two Friesian bulls were carried out by the British Oil and Cake Mills Ltd. at two centres in Britain between 1953 and 1961. The tests followed the Danish pattern: groups of ten to seventeen daughters were brought to the station approximately 6 weeks before first calving and milked under standardized conditions for an average of 270 days.

2. The place of the station system in modern dairy practice in Britain and abroad was discussed.

3. Earlier results had suggested that milk yield, butterfat percentage, S.N.F. percentage, milking rate and conception interval should be taken into account in a progeny test.

4. Correlations were calculated between the bulls 305-day field ratings for milk yield and fat percentage and their 90- and 270-day station assessments. Possible reasons for the discrepancies were investigated.

5. The selection system employed did not appear to lead normally to the choice of heifers whose dams' milk yield or fat percentage differed from the recorded averages for the breed. In two groups of special cases, deviations were apparent but the effect on the accuracy of the station test was shown to be small. It was concluded that bias due to maternal genetic variation was unlikely to be serious in the general case.

Using the continuous infusion isotope dilution technique, the glucose utilization rate has been compared in three groups of sheep on different diets. Glucose was utilized at the mean rate of 1·8 mg./kg./min. on a daily ration containing 126 g. crude protein, at the mean rate of 2·8 mg./kg./min. on a daily ration containing 197 g. crude protein, and at the mean rate of 4·3 mg./kg./min. on a daily ration containing 460 g. crude protein. The mean percentage of expired carbon dioxide that was derived from glucose was 3·5, 6·5 and 8·9 respectively on the three diets.

1. In an experiment conducted for the 3 years 1961-63 on a perennial rye-grass and white clover sward a split-plot design was used to investigate the effects of liquid manure (cow urine + water) and its interactions with various levels of nitrogen, phosphate and potash fertilizers on the yield of herbage and on the botanical composition of the sward.

2. On the average the liquid manure contained 0.26% N, 0.44% K and had a pH of 8.6.

3. The liquid manure treatments supplied 0, 50, 100, 200 and 400 lb. N/acre/year and 0, 87, 174, 349 and 697lb. K/acre/year. The fertilizer nitrogen treatments were 0, 100 and 200lb. N/acre; the potash treatments 0 and 166 lb. P/acre and the phosphate treatments 0 and 66lb. P/acre.

Two sorghum varieties, Dobbs and Bukura Mahemba, were grown in Tanganyika over a wide range of sites, seasons and naturally occurring levels of Striga infestation. Dobbs showed good Striga resistance relative to Bukura Mahemba: In Dobbs there were 9% of the number of witchweed plants above ground as against Bukura Mahemba. (3200 to 37,200 Striga plants per acre): The grain yield of Bukura Mahemba (845 lb./acre) was adversely affected by the Striga. That of Dobbs (1325 lb./acre) was not.

The experiment testing N residues (made on a clay-loam soil) clearly showed that N applied for potatoes benefited the following wheat crop, but that N applied for wheat benefited the following potato crop little. There were no worth-while 1. An experiment on a clay-loam soil measured responses to three amounts of nitrogen on alternate crops of wheat and potatoes; these dressings were tested in all combinations with three rates of N applied 1 and 2 years previously. Nitrogen applied for potatoes consistently increased yields of following wheat. The residue from applying 1·5 cwt. N/acre for potatoes was equivalent to topdressing the wheat with 0·55 cwt. N/acre; the value of the residue was decreased by applying N to the wheat. Potato yields were increased little by applying N to the preceding wheat crop and the residues were of little significance when compared with the responses to new N. There was no gain from N applied 2 years previously for either crop.

1. In 1959 a concentrated granular fertilizer (15% N, 10% P2O5, 20% K2O) was compared with an equivalent mixture of ammonium sulphate, superphosphate and muriate of potash (each supplying 0·75 or 1·50 cwt. N/acre) for potatoes. At Rothamsted (on heavy soil) the two fertilizers gave similar yields, but at Woburn (on light soil) the larger dressing of the concentrated fertilizer gave about 1 ton/acre more potatoes. In similar barley experiments a concentrated granular fertilizer (20% N, 10% P2O5, 10% K2O) was compared with a dilute granular fertilizer (12% N, 6% P2O5, 6% K2O); each was combine-drilled to supply 0·3 or 0·6 cwt. N/acre. At Rothamsted the two fertilizers gave identical yields, but at Woburn the concentrated fertilizer (at the double rate) gave significantly more grain.